Rubber stopper



FIG. 1 is a perspective view of a rubber stopper showing my new design;

FIG. 2 is a top view thereof;

FIG. 3 is a side view thereof;

FIG. 4 is a bottom view thereof; and,

FIG. 5 is a cross-sectional view thereof taken in the direction of thearrows along line 5--5 of FIG. 2.

The ornamental design for a rubber stopper, as shown.